The present invention relates to improvements in pipe sections having couplings on the end thereof. In another aspect, this invention relates to an improved pipe section having couplings which allow at least one full turn of a relative axial rotation between connected sections while providing effective sealing. According to another aspect the present invention relates to an improved pipe section having indicia thereon for indicating proper engagement of the sections. According to even further aspect, this invention relates to an improved pipe section having a required makeup torque for effective sealing which is in the range of application by hand by one worker without the necessity of using equipment, tools and the like.
In the provision of piping systems such as in oilfield flow line pipe applications, it has been common to use pipe sections having threaded couplings on the end thereof for interconnecting the sections to form the system. It has also been typical to utilize pipe sections formed from resin impregnated filament wound materials to form the pipe sections such as is disclosed in the U.S. patents to McLarty, No. 3,572,392, issued Mar. 23, 1971; Carter, et al., No. 3,784,239, issued Jan. 8, 1974; and Meher, No. 3,540,757, issued Nov. 17, 1970. These filament wound sections have proved particularly advantageous for use in an oilfield flow line pipe environment because of their light weight, ability to withstand the pressure ranges of this use and because of their non-corrosive nature.
The use of non-corrosive pipe sections has been hindered by problems present in effectively joining the sections of pipe together. One method of assembling the same is to lay the sections of pipe at the place of intended use and then connect the sections by bonding with adhesive.
This method of assembly poses problems such as the necessity of forming a complete bond between the sections to provide an effective seal and the necessity of waiting while one bond is taking place before the next section can be positioned and connected. In addition, these connections are made under less than ideal conditions wherein contamination may reduce the integrity of these connections.
To eliminate these bonded joints, systems such as is disclosed in the U.S. patent to Carter, No. 3,784,239, have been attempted wherein threaded connections are made to couple the sections together.
The sections using threaded connections also possess problems in that resin impregnated filament pipe sections do not lend themselves well to the use of wrenches. When wrenches are used they tend to compress the pipe, which may result in damage to the pipe that would later cause a failure of the section. In addition, it is sometimes necessary to utilize fittings in the pipe sections such as an elbow to make a right hand turn in the pipe system. It has been found that it is extremely difficult to provide effective sealing between these screw type joints while orientating the fitting in the required direction. One method that has been attempted to alleviate this problem is to cut a section of pipe and bond an elbow or another type of fitting to the end thereof. Unless this bonding is accomplished after the pipe is installed the orientation of the fitting in the proper direction cannot be assured. In addition, if the bond is formed after the section is coupled the additional risk of contamination of the bond occurs.
Thus, although these resin impregnated filament pipe sections have advantages, they are very difficult to use and install.